940B - Our Tanya is Crying Out Loud - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
#define ll long long int
long long int mod= 1e9+7;

int main(){

ll n,k,a,b;
cin>>n>>k>>a>>b;
ll ans=0;
if(n<k){
   cout<<a*n-a;
   return 0;
}
else if(n==k){
   cout<<min(n*a-a,b);
   return 0;
}else if(k==1){
   cout<<(n-1)*a;
   return 0;
}

 while(n>1){
   if(n%k==0){
      ll tem=n/k;
      ll cost=0;
      if(tem==1)cost=(k-1)*a;
      else cost=(n-tem)*a;
      ans+=min(b,cost);
      n/=k;
   }else{
      ll x=n/k;

      ll tem=x*k;
      if(tem==0)tem++;
      ans+=(n-tem)*a;
      n=tem;
   }
   // cout<<ans<<" ";
 }
 cout<<ans;
    return 0;
}